1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a method of producing the electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each including the electrophotographic photosensitive member. The present invention also relates to a urea compound.
2. Description of the Related Art
One example of an electrophotographic photosensitive member installed in an electrophotographic apparatus is an organic electrophotographic photosensitive member containing an organic photoconductive substance (charge generating substance) (hereinafter referred to simply as an “electrophotographic photosensitive member”). Electrophotographic photosensitive members have been widely studied. In particular, for the purpose of extending the life of an electrophotographic photosensitive member and improving image quality, attempts are being made to improve the durability of the electrophotographic photosensitive member.
The improvement of the durability of the electrophotographic photosensitive member may be an improvement of mechanical durability, such as resistance to abrasion and scratches, an improvement of electric potential stability during repeated charging and discharging of electricity, or the prevention of image deletion caused by discharge products. There is a demand for an electrophotographic photosensitive member that satisfies both the improvements of mechanical durability and electric potential stability and the prevention of image deletion in order to achieve an electrophotographic photosensitive member having excellent image stability.
Japanese Patent Laid-Open No. 2000-066425 discloses a technique for providing a surface layer with a polymer produced by the polymerization of a charge transporting substance having two or more chain-polymerizable functional groups. This technique can improve the mechanical durability (abrasion resistance) and the electric potential stability of the electrophotographic photosensitive member. However, the electrophotographic photosensitive member having high abrasion resistance described in Japanese Patent Laid-Open No. 2000-066425 tends to have discharge products (ozone and nitrogen oxide) deposited thereon and cause image deletion in a high temperature and high humidity environment.
Image deletion may be reduced by using an electrophotographic photosensitive member that contains an additive agent. Japanese Patent Laid-Open No. 63-097959 proposes the addition of a urea compound to a photosensitive layer to prevent deterioration of an electrophotographic photosensitive member caused by an active gas.
There is another technique for using a chain-polymerizable additive agent to maintain high mechanical durability of a surface layer that contains a polymer (curable resin) produced by the polymerization of a charge transporting substance having a chain-polymerizable functional group. More specifically, various chain-polymerizable siloxane compounds are used to improve cleaning of the surface of an electrophotographic photosensitive member. Japanese Patent Laid-Open No. 2005-115353 proposes a method of adding a reactive silicone compound that has a dimethylsiloxane structure as a repeating unit. Japanese Patent Laid-Open No. 2006-047949 proposes a method of dispersing an acryl-modified polyorganosiloxane having radical reactivity in a radical polymerizable monomer.
However, the present inventors found that the urea compound described in Japanese Patent Laid-Open No. 63-097959 has an insufficient image deletion preventing effect and tends to decrease electric potential stability. The reactive silicone compound described in Japanese Patent Laid-Open No. 2005-115353 tends to cause film defects because of an insufficient affinity between the dimethylsiloxane structure and a charge transporting substance having an aryl group. Although its dimethylsiloxane structure improves cleaning of the surface of an electrophotographic photosensitive member, the acryl-modified polyorganosiloxane described in Japanese Patent Laid-Open No. 2006-047949 insufficiently prevents image deletion and tends to decrease electric potential stability.